Posts Tagged ‘x-ray’

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Trick or Treat!

October 30, 2011

What lurks inside these beguiling treats?

A razorblade, perhaps?

Or a sewing needle?

Time for another Halloween in America, and you know what that means: some good ol’ fearmongering about dangerous strangers who are hell-bent on kidnapping, raping, and chainsaw-murdering your darling little moppets! Oh joy. Perhaps no trope of the “stranger danger” variety is more firmly ensconced in the contemporary American Halloween lore than the idea of the devious misanthrope who slips razor blades into apples or needles into candy bars before passing them out to trick-or-treaters.  Concern persists despite scant evidence for such activity.  The fear had reached its zenith by the mid-’80s following the Chicago Tylenol Murders of ’82.  By 1988, the city of Reno, NV was spending about $1630 per annum to x-ray trick-or-treaters’ loot in the radiology wards of its three hospitals, as an article by J. Calvanese in Veterinary and Human Toxicology reported. “No films were positive for radio-opaque foreign bodies.” Despite a near-zero incidence of such tampering, it is still common for establishments with x-ray equipment to operate it for paranoid Halloweeners.

Tonight I offer you a couple low-energy radiographs of compromised “treats” prepared with great care in my kitchen (click any image for a high-res version). Typical dental and medical x-ray equipment operating in the 80-120 kVp range has difficulty producing high contrast for the objects pictured here, so I recommend a mammography or extremity type of tube operated at a low voltage. These photos were taken at 26 kVp with the tube and screen shown.  The screen was 5 feet downstream of the tube, where the exposure rate was about 100 roentgen / hour. The photos of the screen were made with my Panasonic LX5 point-and-shoot at ISO200 / f2.1 / 30-40 seconds. Happy Halloween…and remember, your kids are far more likely meet a grisly end in a traffic accident driving to the hospital / police station / courthouse to x-ray their candy, than they are from the candy itself.

At top: beryllium-window x-ray tube used in these images.

At bottom: the diverging x-ray beam from the tube’s window impinges on the CdZnS fluoroscopy screen used to take these images.

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Scintillation Crystals and X-Rays

May 7, 2008

Here are a few photos of inorganic scintillators glowing from exposure to a ~ 300 R / hr x-ray field. These were all long digital exposures, 5-15 seconds, taken last year, and all had to be de-speckled extensively due to radiation noise on the camera CCD.

Bismuth germanate (BGO) crystals from a PET scanner. Lovely cyan glow, not particularly well-matched to photomultiplier tubes but gorgeous to the human eye. Dense, and a wicked photoabsorber of gamma rays, BGO is well-suited to portable homebrew scintillation detectors.

Barium fluoride, a material of choice for fast pulse-mode gamma detectors. Much of the light emission is in the ultraviolet, and to the eye the glow appears a deep purple color. Perhaps there’s a use for this in fast neutron detectors based on inelastic scattering on F-19?

Sodium iodide doped with thallium (NaI:Tl), the old standard for gamma spectrometry and high-class uranium prospecting. This 3″ x 1″ crystal is hermetically sealed because the NaI is hygroscopic. The rich blue glow resulting from exposure to a 60 microcurie radium source is literally bright enough to read by. Next to the x-ray machine, it shines like a spotlight!

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